An Examination of Surface Melt Inducing Atmospheric Rivers over the Antarctic Peninsula

Atmospheric rivers (ARs) are regions of extra-tropical cyclones that can bring significant amounts of heat and moisture to the coastal environments where they make landfall. They are characterized by a narrow, river-like stream of clouds with significant amounts of water vapor transported within. They occur worldwide, and have been observed to be increasing in intensity as a result of anthropogenic climate change. On the Antarctic Peninsula (AP), ARs have been shown to induce substantial surface melt events, even in the austral winter, indicating that there is a theoretical link between ARs and ice shelf stability. However, not all ARs that impact the AP induce surface melt events, indicating the importance of improving our understanding of the atmospheric conditions present during surface melt-inducing AR events. In this study, we use the 2015 Guan and Waliser algorithm to detect AR events on the Larsen C ice shelf. Once identified, we used both passive (NOAA’s Special Sensor Microwave/Imager (SSM/I)) and active (NOAA’s Advanced Scatterometer (ASCAT)) satellite surface melt observations to determine if the AR induced a surface melt event. Within the 2015-2019 sample period, we identified 9 non-austral summer (March - November) ARs that induced a surface melt event, then selected 9 other non-melt-inducing AR events of similar duration and seasonality. Using ERA5 reanalysis datasets, we compared 2-meter temperature, 10-meter wind data, and 500mb geopotential height during melt-inducing ARs with their non-melt-inducing counterparts. We observed that melt-inducing ARs are associated with a stronger high/low pressure couplet, with a 500mb ridge axis located west of the AP at AR landfall. We also found that melt-inducing ARs have stronger northwesterly flow throughout their duration and increased post-AR Larsen C surface temperatures, when compared with non-melt-inducing ARs. These results illustrate the general atmospheric conditions present within non-austral summer melt-inducing ARs, allowing us to identify, analyze, and potentially forecast future AR events that may induce melt and theoretically threaten the stability of the AP’s ice shelves.